1. Field of Invention
This invention pertains to a skimmer for removing surface contaminates from the top layer of a body of liquid. More particularly, this invention pertains to a surface skimmer that compensates for changes in fluid level while maintaining a constant flow of fluid.
2. Description of the Related Art
Various types of skimmers are known in the art, including disk, drum, and those with flotation devices. With respect to the skimmers that operate with varying water levels, there are two types of skimmers: those that are adjusted, either manually or automatically, to the water level and those that use floats to compensate for changes in water level. An example of an adjustable skimmer is disclosed in U.S. Pat. No. 4,693,821, titled “Weir for waste water treatment systems.”
Of the second type of skimmer that uses flotation devices, there are two different classes of float type skimmers. The first class are those that use the float solely to position the skimmer inlet near the surface of the water. The second class are those that have a float that compensates for the water level and for the flow rate of the skimmer.
There are examples of the first class, which use floats only to compensate for water level changes. U.S. Pat. Nos. 1,032,458; 5,059,312; 5,498,348; and 5,897,773 illustrate examples of devices within the first class. There are examples of the second class in which the skimmer compensates for not only the water level but for the rate of flow from the skimmer. For example, U.S. Pat. No. 2,608,300 discloses a floating, pivoting tank with a weir. When the flow out of the device exceeds the liquid flow over the weir, the tank pivots such that the weir is lowered, thereby causing more liquid to flow over the weir and into the tank.
U.S. Pat. No. 3,702,134 discloses a skimming apparatus 10 with an inlet 18 at one end of a pivoting assembly. Opposite the inlet 18 is a counterbalancing duct 26 that is open to the atmosphere through a vent line 32. When the flow through the inlet 18 is less than the outlet flow of the skimming apparatus 10, the fluid in the counterbalancing duct 26 decreases and causes the inlet 18 to lower into the fluid whereby more fluid enters the inlet 18 and flows into the counterbalancing duct 26.
U.S. Pat. No. 4,085,049 discloses a skimming device 10 with a floating frame 12 and an open-sided cylinder 24. The cylinder 24 rotates about a pivot point 8 that is offset towards the open weir edge 26. As the cylinder 24 fills with fluid, the cylinder 24 rotates, thereby causing the weir edge 26 to rise relative to the surface of the fluid. As the fluid in the cylinder 24 is pumped out, the cylinder 24 empties and rotates such that the weir edge 26 is lowered into the fluid.
U.S. Pat. No. 4,288,324 discloses a skimming system 10 with a truncated ovoidal-shaped compartment 16 that has a horizontal pivotal axis 20 that moves a lip 17 up or down depending upon the amount of fluid contained in the compartment 16. When the fluid is removed from the compartment 16 faster than the fluid flows over the lip 17, the fluid level in the compartment 16 drops, causing the compartment 16 to rotate and the lip 17 to move lower, thereby allowing more fluid to enter the compartment 16.
U.S. Pat. No. 4,405,458 discloses a weir collar 1 that is nested within a fixed guide collar 2. Inside the weir collar 1 is a float chamber 4 that allows the weir collar 1 to slide within the fixed guide collar 2 such that the top edge of the weir collar 1 is even with the level of the fluid 14 inside the fixed guide collar 2 and the weir collar 1.
U.S. Pat. No. 4,554,079 discloses a cylindrical collection chamber 3 with a front pod 9 and a rear pod 13. The pods are mounted below the waterline. The front pod 9 is sealed, but the rear pod 13 is in fluid communication with the collection chamber 3. The collection chamber 3 has an inlet 5 in the front of the chamber 3. As the chamber 3 and the rear pod 13 fill with fluid, the rear pod 13 looses buoyancy, causing the collection chamber 3 to rotate such that the inlet 5 is elevated above the waterline. The collected fluid is removed from the device 1, thereby causing the inlet 5 to rotate towards the waterline so that the collection chamber 3 can refill with fluid.
U.S. Pat. No. 5,601,705 discloses a skimmer 12 that includes one float 76 for compensating for varying fluid levels and second float 58 for adjusting for rate of flow through the skimmer 12. The second float 58 operates within a chamber 30 and causes an intake pipe 48 to rotate, thereby varying the size of the inlet 86.
U.S. Pat. No. 6,287,460 discloses a collecting container 1 with triangular side walls 5 and 6. The collecting container 1 is tiltable and has a pipe 7 for removing collected fluid. As the collecting container 1 fills with fluid, the container 1 tilts because the back end loses buoyancy and the front end lifts out of the fluid, thereby limiting the flow of fluid into the container 1. As the fluid is pumped out of the container 1, the container 1 gains buoyancy and the container 1 tilts such that the fluid flow into the container 1 increases.
U.S. Pat. No. 6,488,841 discloses a skimmer with two floats 60, 62 that follow the fluid level as it varies. Another float 86 is inside a supply container 72 and operates an adjuster 80 that varies the size of an inlet 76. As the pump 34 draws down the fluid level in the container 72, the float 86 causes the adjuster 80 to fall, thereby increasing the size of the inlet 76 and filling the container 72 and maintaining a supply of fluid to the pump 34.